More than three years after Rihanna was assaulted by Chris Brown, the singer continues to reflect the incident and its aftermath, saying she felt "protective" and "concerned about" her ex-boyfriend. "As angry as I was – as angry and hurt and betrayed," Rihanna told Oprah Winfrey, "I just felt like he made that mistake because he needed help."

In the new interview, due to air in the US on Sunday, Rihanna said she was afraid of what would happen to Brown after the incident became public. "It became a circus and I felt protective," the singer explained. "Who's gonna help him? Nobody's gonna say he needs help. Everybody's gonna say he's a monster without looking at the source."

After initially denying the charges, Brown eventually pleaded guilty to assaulting Rihanna in the early hours of 8 February 2009. According to the police report, the couple got into an argument after Rihanna found a text message on Brown's phone, sent by an ex-girlfriend. Brown tried to force Rihanna out of his car before punching her repeatedly in the face, causing bleeding. After throwing her phone out of the window, he continued to punch the pop star's arms, hands and legs, biting her ear and hands, and twice placing her in a headlock. Police were called after a witness heard Rihanna's screams.

"It was a weird, confusing space to be in," Rihanna said this week. "I felt like the only person they [hated was] him." Brown, who grew up in an abusive household, was sentenced to one year's probation and domestic violence counselling. "It was embarrassing, it was humiliating," Rihanna said. "I lost my best friend. Everything I knew switched, switched in a night, and I couldn't control that."

Though Brown's career initially suffered, it has since bounced back. He and Rihanna collaborated on two songs earlier this year, and the 23-year-old won his first Grammy. On Wednesday Brown was named as co-defendant in a $16m (£10.2m) lawsuit, brought by a New York nightclub; the owners allege Brown and the rapper Drake caused a massive brawl after arguing about Rihanna. Seven people, including a professional basketball player, were injured.